Hepatitis C virus is the leading cause of chronic liver disease worldwide and has become a focus of considerable medical research. HCV is a member of the Flaviviridae family of viruses in the hepacivirus genus, and is closely related to the flavivirus genus, which includes a number of viruses implicated in human disease, such as dengue virus and yellow fever virus, and to the animal pestivirus family, which includes bovine viral diarrhea virus (BVDV).
There are 6 major HCV genotypes and more than 50 subtypes, which are differently distributed geographically. HCV type 1 is the predominant genotype in the US and Europe. For instance, HCV type 1 accounts for 70 to 75 percent of all HCV infections in the United States. The extensive genetic heterogeneity of HCV has important diagnostic and clinical implications, perhaps explaining difficulties in vaccine development and the lack of response to therapy. An estimated 170 million persons worldwide are infected with hepatitis C virus (HCV).
HCV replicates preferentially in hepatocytes but is not directly cytopathic, leading to persistent infection. In particular, the lack of a vigorous T-lymphocyte response and the high propensity of the virus to mutate appear to promote a high rate of chronic infection. As such, subsequent to an initial acute infection, a majority of infected individuals develop chronic hepatitis, which can progress to liver fibrosis leading to cirrhosis, end-stage liver disease, and HCC (hepatocellular carcinoma) (National Institutes of Health Consensus Development Conference Statement: Management of Hepatitis C. Hepatology, 36, 5 Suppl. S3-S20, 2002).
Transmission of HCV can occur through contact with contaminated blood or blood products, for example following blood transfusion or intravenous drug use. After initial exposure to the Hepatitis C virus, HCV RNA can be detected in blood in 1-3 weeks. Within an average of 50 days virtually all patients develop liver cell injury. The majority of patients are asymptomatic and anicteric. Only 25-35 percent develop malaise, weakness, or anorexia, and some become icteric. Antibodies to HCV (anti-HCV) almost invariably become detectable during the course of illness. Anti-HCV can be detected in 50-70 percent of patients at the onset of symptoms and in approximately 90 percent of patients 3 months after onset of infection. HCV infection is self-limited in only 15 percent of cases. Recovery is characterized by disappearance of HCV RNA from blood and return of liver enzymes to normal.
About 85 percent of HCV-infected individuals fail to clear the virus by 6 months and develop chronic hepatitis with persistent, although sometimes intermittent, viremia. This capacity to produce chronic hepatitis is one of the most striking features of HCV infection. Chronic hepatitis C is typically an insidious process, progressing, if at all, at a slow rate without symptoms or physical signs in the majority of patients during the first two decades after infection. Symptoms first appear in many patients with chronic hepatitis C at the time of development of advanced liver disease.
In chronic hepatitis, inflammatory cells infiltrate the portal tracts and may also collect in small clusters in the parenchyma. The latter instance is usually accompanied by focal liver cell necrosis. The margin of the parenchyma and portal tracts may become inflamed, with liver cell necrosis at this site (interface hepatitis). If and when the disease progresses, the inflammation and liver cell death may lead to fibrosis. Mild fibrosis is confined to the portal tracts and immediately adjacent parenchyma. More severe fibrosis leads to bridging between portal tracts and between portal tracts and hepatic veins. Such fibrosis can progress to cirrhosis, defined as a state of diffuse fibrosis in which fibrous septae separate clusters of liver cells into nodules. The extent of fibrosis determines the stage of disease and can be reliably assessed. Severe fibrosis and necroinflammatory changes predict progression to cirrhosis. Once cirrhosis is established, complications can ensue that are secondary to liver failure and/or to portal hypertension, such as jaundice, ascites, variceal hemorrhage, and encephalopathy. The development of any of these complications marks the transition from a compensated to a decompensated cirrhosis.
Chronic hepatitis C infection leads to cirrhosis in at least 20 percent of patients within 2 decades of the onset of infection. Cirrhosis and end-stage liver disease may occasionally develop rapidly, especially among patients with concomitant alcohol use. Chronic infection by HCV is associated with an increased risk of liver cancer. The prevailing concept is that hepatocellular carcinoma (HCC) occurs against a background of inflammation and regeneration associated with chronic hepatitis over the course of approximately 3 or more decades. Most cases of HCV-related HCC occur in the presence of cirrhosis.
Liver fibrosis is one of the processes that occurs when the liver is damaged. Such damage may be the result of viral activity as explained hereinabove (e.g., chronic hepatitis types B or C) or other liver infections (e.g., parasites, bacteria); chemicals (e.g., pharmaceuticals, recreational drugs, excessive alcohol, exposure to pollutants); immune processes (e.g., autoimmune hepatitis); metabolic disorders (e.g., lipid, glycogen, or metal storage disorders); or cancer growth (primary or secondary liver cancer). Fibrosis is both a sign of liver damage and a potential contributor to liver failure via progressive cirrhosis of the liver.
It has been disclosed that the inhibition of the family of TGFβ kinases is useful in the treatment of fibroproliferative disorders, including liver fibrosis. However, as it is noted above, liver fibrosis may be caused by different etiological agents, including the Hepatitis C virus. Most importantly, liver fibrosis is a specific condition in the disease progression of patients infected with HCV.
WO04/024159 discloses substituted pyrimidines and triazines which are useful in the treatment of conditions associated with enhanced TGFβ activity.
It has been surprisingly found that the compounds of the present invention inhibit HCV replication. HCV replication refers to the process of reproducing or making copies of HCV RNA. In the present invention HCV replication both refers to the replication of the HCV virus as a whole or the replication of the HCV RNA genome.
The compounds of the present invention are thus able to treat HCV infected patients at early stages in order to avoid disease progression, thereby avoiding that the patient develops chronic hepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma (HCC), or death.
In addition, the compounds of the invention are valuable in that they can diminish the HCV viral load of a patient, or can diminish the HCV viral load of a patient to undetected levels.
The compounds of the invention herein are derivatives of pyrimidine. PCT publication WO01/47921 describes pyrimidine and triazine compounds that are inhibitors of kinase activities associated with various inflammatory conditions, as opposed to the treatment of fibroproliferative disorders described herein. The above mentioned PCT publication describes the use of the compounds disclosed only for treatment of the inflammatory aspects of certain autoimmune diseases. Further, the compounds described differ from those described herein by virtue of the substitutions required on the pyrimidine nucleus; among other distinctions, the compounds disclosed in the PCT publication do not include phenyl bound directly to the pyrimidine ring.
Related compounds, some of which have the 4-pyridylamine group at C-4 on the pyrimidine, are disclosed in published U.S. Patent Applications, publications no. US 2004-0132730 A1, US 2004-0132159-A1 and US 2005/0004143-A1. Those applications, however, disclose a preference for certain electron-donating substituents on the pyridine ring of the 4-pyridylamine group, including alkyl, amine and alkoxy groups, without disclosing a preferred position for those substituents, or they suggest a variety of aryl groups which may be pyridyl for the 4-position substituent on a pyrimidine ring but do not disclose or suggest the combination of features of the present invention, in particular they do not suggest the amides of the present invention. The present invention provides compounds specifically including a 4-pyridylamine that is substituted by a carboxamide group which is attached at position 3 on the pyridine ring. The carboxamide is attached via its carbonyl carbon, and is typically a secondary amide; furthermore, the compounds of the present invention include specific functional groups and substituents particularly on the amide group, that are selected for their ability to reduce metabolism and increase bioavailability of the active species.
U.S. Pat. No. 6,476,031 ('031) also discloses compounds containing a quinazoline ring linked to an aryl group at C-4 of the quinazoline. The compounds are reported to act at the TGFβ site, and some of the compounds include a 4-pyridylamine group at C-4 of the quinazoline. However, the '031 patent discloses that the aryl group linked to C-4 of the quinazoline is preferably unsubstituted 4-pyridyl, and it does not disclose any compounds where the 4-pyridyl includes an amide substituent such as the ones at the 3-position of the 4-pyridyl group in the compounds of the present invention.